| 摘要 |
PROBLEM TO BE SOLVED: To provide a projection image display device capable of maintaining the brightness of a projected image at a desired level even when lamp voltage is changed over a wide range and further variation is found in the light emitting efficiency of a lamp itself and the characteristic of the optical system of the image display device. SOLUTION: The projection image display device where power is supplied to a light source lamp through a ballast is provided with a power control means constituted to supply the power of a value in accordance with the amplitude of a control signal applied to the control signal input terminal of the ballast to the light source lamp, and generating a power switching signal whose amplitude is changed in a fixed cycle between two different values and whose duty A/(A+B) is varied as the control signal. COPYRIGHT: (C)2004,JPO&NCIPI |
